PROJECT SUMMARY Starting from a blueprint of the cell, including a map of its signaling cables, we now face the monumental challenge of understanding how signals flow in these cables and deciphering cellular information transmission protocols. One particularly daunting problem is that cells often use shared pathways (the same cables) to transmit different signals, yet have an exquisite capacity to specifically interpret these signals. How cells encode information and then decode it with high fidelity to optimize the use of shared signaling channels remains largely unknown. Uncovering these strategies requires synergy between a unique multidisciplinary toolkit of technology, computational modeling, and high resolution/high throughput experimental investigations. Using Protein Kinase A (PKA), an important biological signaling hub, and our unique multidisciplinary approach, we will dissect the mechanisms by which different inputs are encoded by the PKA channel in S. cerevisiae and then decoded by downstream transcription factors and genes. We will investigate the repercussions of errors in such signal encoding and decoding schemes, and by doing so, we will be able to extract fundamental principles that cells use to circumvent their information transmission bottlenecks. Fundamentally, these investigations will provide a comprehensive and quantitative portrait of the dynamic operation of the PKA pathway as an integrated system, and a detailed synopsis of its failure modes and their connections to cellular physiology. Our experimental design will also generate a catalogue of the connectivity of PKA to the rest of the cellular chassis.